ERD-AlLARMS FOR FLYERS.
RESULTS OF OUR COMPETITION.
OF the^ hundred or so designs submitted for our Speed Alarm
Competition, forty-two were provisionally approved, and of these
we have finally selected five that we are forced to declare equal
in merit. Had it been possible, we should have preferred to
award the prize for one design only, but the circumstances of the
case in our opinion prevent this, and the result is that five com
petitors share the award.
Fundamentally, the reason why this is so is because no competitor
has, so far as we are aware, taken any definite steps to have his
ideas put to a practical test, which according to the terms of the
competition would have been taken into consideration. We had,
therefore, necessarily to judge the merits of different designs purely
on their plausibility, and in the light of common knowledge in
matters relating to constructive detail. As a result of this necessity,
it has been essential to regard certain entirely different sound
instruments as potentially equal in merit, on the grounds that
either one of them would sufficiently serve the purpose required
of it. Such, for example, is the case with the whistle, the bell or
gong, and the siren. On the other hand, in the absence of any
evidence to show that such simple and well-recognised devices are
unsuitable, there is no particular purpose in going out of the way to
introduce other principles such as those underlying the action of the
musical box or the gramophone, but we do not thereby suggest that
such schemes would not work.
Then, apart from the sound instrument itself there is its operation
to be considered, and again it is necessary to recognise as equally
meritorious the employment of air pressure on a plane, and the use
of the rotation of a propeller windmill. Both are plausibly suitable
for the purpose required. In connection with the propeller wind
mill, which is essentially a rotary movement, the introduction of
some form of centrifugal governor is more or less a necessity, and
may be considered as an incidental part of the system not calling for
special recognition on its own account. Thus we have three distinct
sound instruments, and two distinct principles of operation that it
has seemed to us only fair to recognise as being on a potentially
equal footing, and as we have been unable to find any one instru
ment in either category that deserves to stand out above others in
another category we have decided, as already mentioned, to divide
the prize in the following way :—
The question of a multiple note alarm, which was suggested
initially as being preferable, other things being equal, has not met
IN any engine the following factors must be observed to
eliminate vibration.
I. The centre of gravity of the moving parts should remain
stationary. 2. The turning moment must be constant and
always positive.
The former condition can be arrived at fairly satisfactorily ;
but the latter can only be obtained by employing a sufficient
number of cylinders or impulses in comparison to the number
of revolutions in the crank-shaft in the same interval of
time. By so doing we can obtain a fairly constant torque,
but the fact must not be lost sight of that the application
of the thrust to the crank-shaft must be so arranged that no
longitudinal period of vibration is set up.
We have in the purely radial engine no difficulties of
longitudinal vibration, as the application of load is all in the
same plane and we at once overcome what was at one time
a source of some trouble, viz., want of longitudinal balance.
Secondly, in the radial engine, balance in other directions
is not a difficult matter, and though perfect running balance
may not be obtained, the centre of gravity of the moving
parts moves in a circular path and does not violently oscillate.
If one considers the working of the four-cycle motor it will
be noticed immediately that production of energy is only
obtained during one stroke of the piston in four ; also, all
parts which serve to transmit the power—that is, the connect
ing-rod and crank-shaft—actually do their full work only
during the explosion period for which they are calculated.
This is a very small fraction of the working stroke, and still
smaller of the complete cycle.
We have, therefore, in the radial design several cylinders
operating the same crank-pin, and we adopt the disposition
* Abstract of a paper read by Mr. R. W. A. Brewer before the Aviation
Section of the AA. and M.U.
with any really satisfactory solution in the competitive designs, and
under the circumstances our awards all go to the simple alarms
that best fulfil the primary conditions of making one distinctive sound.
The awards are as follow :—
Whistle.—No. 31, G. Boocock (published December 17th), for
the best design of whistle. The merit in this design lies in its
simplrcity and in the introduction of the inclined plane for operating
a rotary grid valve, which type of valve is well suited for closing a
large orifice with a very small movement. The use of the pressure
plane in this manner, although only crudely represented in the com
petitor's sketch, lends itself to a suitable arrangement.
Siren.—No. 37, \V. Langdon-Davies (published December 24th),
for the best siren. The merit in this design lies in its simplicity and
in the control of the conditions under which the siren operates.
The siren is released by a pressure plate at the required s^eed and
the construction of the members of the sound instrument therein
form their own propelling mechanism.
Gong.—No. 16, E. V. Gratze (published September 24th), for
the best mechanical bell or gong. The merit in this design lies in
its compact arrangement and in the well-considered disposition of
its parts.
Systems of Control.—Propeller. No. 41, A. E. Rutherford
(published December 31st), for the best design of propeller con
trolled apparatus. The merit of this design lies in its compactness,
and particularly in the use of a form of governor that has generally
proved itself superior in instruments of an allied character, such as
speed indicators for motor cars. The apparatus, as shown, controls
the ringing of an electric bell.
Pressure Plate.—No. 27, W. Read (published November 26th),
for the best design of pressure-plate control. The merit in this
design lies in the idea of using two plates of opposite inclination
opening under the pressure of the wind like swing doors in a passage.
This idea is doubtless superior to a system employing a single plate,
as it would seem less liable to be affected by extraneous conditions,
inasmuch as both plates have to open equally to effect the control,
which in this case consists of closing the electric circuit of an electric
bell. Accidental movement of the instrument to one side or the
other might jerk one plate against the contact, but it would not
probably jerk both plates in opposite directions simultaneously.
The above-mentioned prize winners are requested to communicate
with the Editor.
of the said cylinders in star fashion around the crank-shaft
of spiral shape.
To reduce the variations of the couple to a minimum it
is necessary that the explosions in the different cylinders
of such an arrangement succeed each other in absolutely
equal intervals, and therefore as unequal number of cylinders
must be taken with a minimum of five. The ignition as well
has to take place in such a manner that those numbered
2 and 4 fire first, and those unequally numbered afterwards,
that is, at the second revolution of the cycle.
The object of a designer is to obtain the greatest possible
ratio of cylinder volume to total volume of engine, and in
radial construction we have the nearest approach in this
respect to the turbine. The complete engine in star shape
gives a symmetrical appearance. However, in actual prac
tice this arrangement produces several difficulties, which,
although already solved, appear insurmountable. For
instance, if we imagine the cylinders separated by a horizontal
line passing through the axis of the crank-shaft and we then
turn the lower part of the engine about 1800, the cylinders
which were below the horizontal line would come above it
and fit between the others. Those would be connected to
another crank-pin at 180° from the first.
This gives exactly the same turning effect as a truly star-
shaped engine and renders lubrication by splash a much
simpler problem. The semi-star-shaped engine has another
advantage, viz., that it facilitates air-cooling by means of
radiating ribs.
This method of cooling in aero-motors has been fully
proved, and presents the great advantages of lightness and
simplicity. All water-pipes, the radiator, circulating pump,
complicated joints, &c, are done away with in company
with their weight and tendency to leakage.
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RADIAL ENGINES.
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